What is the color of the aqueous solution of $[Co(NH_3)_6]^{3+}$?

Which is the incorrect observation?

When aqueous sodium hydroxide is added to an aqueous solution of chromium $(III)$ ions,a green-blue precipitate is first formed which re-dissolves to give a green solution. This green colour is due to

The correct increasing order of stability of the complexes based on $\Delta_o$ value is $:$
$I. \ [Mn(CN)_6]^{3-}$
$II. \ [Co(CN)_6]^{4-}$
$III. \ [Fe(CN)_6]^{4-}$
$IV. \ [Fe(CN)_6]^{3-}$

For the complex $ML_2$,the stepwise formation constants for the reactions:
$M + L \rightleftharpoons ML$
$ML + L \rightleftharpoons ML_2$
are $4$ and $3$ respectively. Hence,the overall stability constant for the reaction:
$M + 2L \rightleftharpoons ML_2$
is:

The correct order of molar conductivity of the following complex compounds in aqueous solution is:
$(I) K[Co(NH_3)_2(NO_2)_4]$
$(II) [Cr(NH_3)_3(NO_2)_3]$
$(III) [Cr(NH_3)_5NO_2]_3[Co(NO_2)_6]_2$
$(IV) Mg[Cr(NH_3)(NO_2)_5]$